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Porsche 928 Twin Turbo

Our roots in the turbocharged Porsche 928 run deep, extending back to the early 1990s.  There is nobody with more experience in building turbocharged Porsche 928s than Kuhn Performance Technologies.  This includes even the big name early tuners from the 1980's.  Our builds include 4.5 liter twin turbos, 4.7 liter twin turbos, and 5.0 liter 32 valve twin turbos (S4 and GT).  Contrary to polular belief, the turbocharger is the best selection for a forced induction system for the Porsche 928. 

Consider our Twin Turbo system for the Porsche 928 offers:

  • The highest specific output of any bolt-on forced induction system available for the 928 produced by anybody, anywhere
  • The widest possible powerband per unit of manifold pressure (compare the charts, the data doesn't lie)
  • An exceptionally well thought through system which offers significant aesthetic appeal
  • The best performance/dollar of any forced induction system avaialble for Porsche 928
  • Proven and documented performance gains
  • Hand crafted quality and aesthetics in a bolt-on package
  • The best possible components available

Our twin turbo system is based on the GT2871R turbocharger from Garrett.  These modern ball-bearing turbochargers allow for fitment of two high performance turbos in the cramped engine bay of the Porsche 928.  While considered "medium" in size, the GT2871R is a very potent turbocharger, specifically when run as twins on a medium displacement V8, like the 928.  Forget all you've read about turbo lag (boost threshold to be more precise) and the like, because our system performs well beyond any other forced induction system available today.  Full manifold pressure is reached before 4,000 RPM and holds strong, resulting in a power curve that is incredibly wide, without killing top-end performance. 

The twin turbo system was proven in 2007 on our test car, a 1988 Porsche 928S4 with over 170,000 miles on the clock at the time of conversion.  The engine ran stock internals in 2007 and it is still running stock internals today, with great success.  Our test car is driven regularly, and sometimes daily for months on end.  Unreliable?  Nope.  Heat problems? None.  Reliable, fun and super-car fast?  You bet!

By the numbers:

  • 8.5 psig: 495 Wheel HP with 470 ft-lbs on the road
  • 12 psig: 572 Wheel HP with 570 ft-lbs on the road
  • Run on 93 octane pump gas...daily.

Consider that any belt driven system available will never match these output numbers at these manifold pressure settings.  A typical belt driven centrifugal system will need about 12 psig to make it to just the 500 wheel power mark.  That means it has to burn more fuel in the process which places more stress on the engine for the same output.  Additionally, even with 40% higher manifold pressure the powerband width of the twin turbo can simply not be matched by the supercharger.  The same holds true for positive displacement style pumps.  While they offer a nice, crisp immediate punch, the midrange and top-end these systems offer will also never match that of the twin turbo.  To get even close with a stroked normally aspirated 928 engine, you will easily spend twice the price of the twin turbo and not get any additional performance.

What's included?

The twin turbo system consists of the following:

  • Twin high energy ceramic coated turbo headers
  • Twin Garrett GT2871R turbos with 0.86 A/R hotsides and hardware
  • New cylinder head exhaust manifold sealing rings
  • New copper plated exhaust nuts
  • Bosch compressor bypass valves
  • Twin split outlet ceramic coated downpipes with hardware
  • Turbo oil collection sumps
  • Turbo wastegate actuators
  • Oil scavenging system with all oil lines and fittings
  • Forced induction plumbing, powder coated
  • All silicone hose and ABA brand hose clamps
  • Proprietary intake plenum box with Porsche and Twin Turbo badges and mounting hardware
  • Wastegate control lines (hard lines)
  • Twin high flow bar and plate intercoolers
  • Patterns and materials to construct intercooler ducting
  • Bumper grills for intercooler integration
  • Modified straps for intercooler integration
  • High flow K&N air filtration system with mounts, filters, and all hardware
  • In block air/oil separator
  • Provent external air/oil separator
  • Water circuit for turbos including post shut down magnetic drive water circulation pump and power circuit
  • Bosch 044 fuel pump with power rely and wiring
  • Increased flow fuel tank pick-up system
  • JDS Porsche Super MAF extended range MAF sensor
  • New Bosch 42 lb/hr fuel injectors
  • New LH 2.3 and EZ-K fuel injection EPROMS (chips)
  • Check valves
  • All braided lines and fittings
  • New vacuum lines
  • New air horn
  • All necessary hardware

In total, there are over 575 individual components which make up the system.  Please consider how extensive our parts list is as you make comparisons to other systems. 

The installation, while lengthy, is basic and straightforward.  Anybody with good mechanical skills can easily install the system.  Expect to spend 40-50 hours doing the installation, possibly less if you own your own lift.  While this may seem lengthy at first glance, consider that once you're done the reward is always there waiting under your right foot.

 

Price: $13,500

© 2011 Kuhn Performance Technologies.